Four Afghans were killed in the accident on the main airport road, according to Kabul's criminal investigations chief, Abdul Ghaafar Sayedzada.
U.S. embassy spokesperson Caitlin Hayden confirmed to CBS News that the SUV involved was carrying four contractors from DynCorp, a private security firm affiliated with the embassy. Afghan police officials said the Americans were traveling in a two-vehicle convoy.
There were conflicting accounts of the accident and its aftermath. Local witnesses told CBS News that the Americans were driving the wrong way down the road, though DynCorp said that version of events was "not correct."
Witnesses also said only three locals were killed in the crash, with the fourth dying after the U.S. contractors opened fire into the crowd.
Hayden, however, denied that any U.S. personnel fired shots during the encounter. Dyncorp also denied the charge, saying in a statement that Americans "took no action against the crowd and did not fire any shots, deferring to the local police who took action to disperse the crowd and remove the [DynCorp] team to safety."
DynCorp further claimed that three of the Americans were hurt by the crowd, including one who received a concussion, before Afghan security forces could help them to safety.
Afghanistan's Interior Minister said police escorted the contractors to the U.S. embassy following the incident. But tension filled the scene hours after the crash.
Afghan police, some carrying riot shields, converged on the area, firing warning shots into the air to disperse the protesters. Sayedzada said the crowd burned two foreigners' vehicles, causing heavy black smoke to rise from the scene.
"It is our right to raise up our voice and protest when innocent Afghans are harmed," said Azizullah, a 25-year-old student, who like many Afghans uses one name.
Ahmad Jawid, who also was at the scene, asked: "Are we not Muslims? Are we not from Afghanistan? Infidels are here and they are ruling us. Why?"
A fatal traffic accident caused by a U.S. military convoy in 2006 triggered an anti-American riot in Kabul that left at least 14 people dead and dozens injured.
In a statement, DynCorp described the fatalities as "tragic" and said an "an investigation into the accident is underway."